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Data Set #016

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About the Data

ABOUT MAUNA LOA CARBON DIOXIDE 1974-1985

Data on the carbon dioxide (CO2) content of the atmosphere at the Mauna Loa Observatory on the Big Island of Hawaii have been measured nearly continuously since the 1950s. A portion of the data are given here, from 1974-1985. Time is expressed in months, with May of 1974 as month 1 (zero was not used to avoid the usual problems with exponential and power law regression). The observatory is at 3,400 m or 11,000 feet above sea level.

The data show both a cyclic behavior and a linear trend. The cyclic behavior corresponds to a yearly cycle of increasing atmospheric CO2 from late fall to spring, with a maximum in May, and then decreasing atmospheric CO2 from spring to late fall, with a minimum in October. The simple interpretation is that carbon dioxide is "scrubbed" or removed from the northern hemisphere atmosphere during the spring-summer growing cycle, when green plants suck up CO2 during photosynthesis. Carbon dioxide is then released during fall and winter, when plants die and rot.

The linear increase of mean yearly atmospheric CO2 with time is actually an exponential increase of mean yearly atmospheric CO2 as measured over a longer time scale beginning in the late 1950s. The yearly increase appears linear because of the short time scale selected for this data set. Fossil fuel consumption appears to be the prime source of this secular increase, with occasional oceanic contributions due to changes in sea surface temperatures associated with currents like El Nino. To see the lastest long-term data, including interpolations for missing values, go to DataSet #078.

Students could find the linear regression for this data set, then subtract that linear increase from the actual data to isolate the cyclic behavior. The cyclic data could then be modelled with simple sinusoidal functions. Notice that there is a "knee" in every yearly cycle from January to December when carbon dioxide concentration does not increase as fast as one might expect. The residuals from the sinusoidal model might prove interesting.

Reference: Komhyr, W. D., Harris, T. B., Waterman, L. S., Chin, J. F. S. and Thoning, K. W. (1989), Atmospheric carbon dioxide at Mauna Loa Observatory 1. NOAA Global monitoring for climatic change measurements with a nondispersive infrared analyzer, 1974-1985; J. Geop. Res., v. 94, no. D6, pp. 8533-8547.

see also:

Thoning et al (1989), "2"; JGR v. 94, pp.

Keeling et al (1976), Tellus v. 28, pp. 538-551.

Martin and Diaz (1991), JGR v. 96, pp. 18689-18704.

Rust etal (1979), JGR v. 84, pp. 3115-3122,

     
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Data from Komhyr et al (1989)
monthly mean CO2 mole fractions from Mauna Loa Observatory
values in ppm

month (num.)

CO2 (ppm)

1

333.15

2

332.07

3

330.99

4

329.17

5

327.39

6

327.25

7

328.50

8

329.51

9

330.69

10

331.41

11

331.84

12

333.26

13

333.92

14

333.39

15

331.81

16

329.90

17

328.56

18

328.45

19

329.29

20

 

21

331.65

22

332.66

23

333.53

24

334.80

25

334.80

26

334.14

27

332.88

28

330.64

29

329.01

30

328.62

31

330.13

32

331.63

33

332.74

34

333.23

35

334.91

36

336.01

37

336.82

38

336.13

39

334.75

40

332.53

41

331.27

42

331.21

43

332.36

44

333.47

45

334.74

46

335.22

47

336.52

48

337.77

49

338.00

50

338.04

51

336.39

52

334.33

53

332.35

54

332.33

55

333.77

56

334.80

57

336.20

58

336.65

59

337.79

60

338.95

61

339.03

62

339.22

63

337.58

64

335.51

65

333.83

66

334.05

67

335.26

68

336.70

69

337.81

70

338.26

71

340.07

72

340.87

73

341.48

74

341.30

75

339.36

76

337.84

77

335.98

78

336.07

79

337.22

80

338.33

81

339.35

82

340.47

83

341.73

84

342.47

85

343.02

86

342.46

87

340.78

88

338.61

89

337.04

90

337.13

91

338.49

92

339.85

93

340.93

94

341.67

95

342.78

96

343.71

97

344.31

98

343.41

99

341.96

100

339.79

101

337.91

102

338.10

103

339.27

104

340.67

105

341.45

106

342.69

107

343.21

108

345.17

109

345.79

110

345.40

111

343.99

112

342.00

113

340.02

114

340.16

115

341.39

116

343.01

117

343.92

118

344.64

119

345.18

120

347.10

121

347.45

122

346.80

123

345.44

124

343.24

125

341.25

126

341.49

127

342.84

128

344.37

129

345.03

130

345.89

131

347.47

132

348.02

133

348.73

134

348.11

135

346.59

136

344.59

137

343.01

138

342.88

139

344.19

140

345.64

 

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